1. Field of the Invention
This invention relates to a mobile multi-function device with the capability of receiving and processing positioning signals, and more particularly, to methods and systems to minimize cost, size and power consumption by sharing resources between the positioning function and the other functions of the device. In a preferred embodiment, one of the other functions is a mobile radio communication terminal.
2. Background Art
Mobile multi-function devices with the capability of determining their geographical location have recently gained popularity. These devices calculate their location by receiving and processing positioning signals, such as GPS signals. In addition, they may incorporate the functionality of other devices such as a mobile radio communication terminal, (e.g. cellular phone), a personal digital assistant (PDA), a multimedia player with music and video reproduction capabilities, etc.
One approach to improve the performance of these devices and to reduce their size, cost and power consumption is to share resources between the positioning function and the other functions of the device. For instance, the GPS-receiver and cellular phone combo device disclosed in U.S. Pat. No. 6,002,363 by Krasner contains a processor that performs all the calculations needed to process GPS signals and all the calculations associated with the cellular phone function.
In difficult environments where some components of the positioning signal are highly attenuated it is necessary to receive and process a long segment of positioning signal in order to attain the required sensitivity. The device disclosed by Krasner stores the received signal (after sampling) in a memory and then carries out all the digital processing of the stored signal in the shared processor. Hence, a drawback of Krasner's device is that a large memory is required to store enough received signal to calculate the location in difficult environment. Another drawback is that the shared processor is occupied with the processing of the positioning signal for a long time during which it is not available for other functions.
What is needed is a method and a system to transform the received positioning signal into a signal with reduced memory requirement so as to reduce the cost, size and power consumption associated with the memory of the device. Also, a method and a system are needed to offload most of the calculations relating to the positioning function from the shared processor so as to increase the availability of the shared processor to the other functions of the device.